Kitabı oku: «Dactylography», sayfa 4

In my Guide to Finger-Print Identification (p. 62) I have advocated uniform enlargement of all such exhibits on the decimal or metric system, and hope that international agreement on this point may be secured. Apart from criminal services its scientific utility would ultimately be very great. The objection that an English jury would dislike being confronted with the technicalities of a foreign and “mathematical” system is very easily met. An English jury – and no jury in the world is fairer or clearer-headed – would only, in any case, have to compare two figures similarly enlarged, one being that of the accused person’s fingers, taken while in custody, and the other, either a similar official record of another date, or a smudgy mark from some blotting-pad, window-pane, drinking-glass, bottle, or the like. The two exhibits, paired for comparison, would have been enlarged exactly on the same scale, whatever that scale might have been. For purposes of judicial comparison, therefore, English terms and English instruments might be used throughout, and no inconvenience could be felt by the most insularly prejudiced jury that could possibly be got together.

When a photographic enlargement has been made, it is necessary to be able readily to test its conformity with the enlargement to be compared with it, or if there be not strict agreement, to allow for and calculate the admitted discrepancy. This may easily be done by an application of the “rule of three.”

Reduced Copy of Police Register Form

Reverse Side of Form

It may be necessary to test the concurrence of curved lines in two exhibits similarly enlarged. At one time I used strips of plumber’s lead, placed edgeways on the curved lines to be compared. They could be flexed so as to show the various sinuosities, however complex, but leaden tapes cannot readily be made to retain the form imparted to them. Copper wire I found to be stiffer, but it readily warps off the plane. An excellent way is to draw on transparent paper a line corresponding to the curved line seen underneath. The transparency is then transferred and adjusted to the other enlargement, the curves of which should be seen to be congruent. The instrument called “flexible curves” which is used by engineers and mechanical draughtsmen I at last tried, and found it to be exceedingly serviceable for such comparisons. The pattern “B,” self-clamping, 12-inch size, is for most cases the most suitable. Other patterns are made also, in sizes of 9 and 18 inches. The “B” pattern has a flexible steel strip, like the lead tape just mentioned. After the curve or series of sinuosities has been adjusted correctly, the shape is rigidly retained by means of a stiff-hinged link-work arrangement attached by tabs. The strip of steel should not be pressed down between two tabs, and when bending or straightening out the instrument one should do so bit by bit, beginning at one end and continuing onwards from there. This useful self-clamping instrument used to be supplied by Mr. Wm. Brooks, scientific instrument maker, 33 Fitzroy Street, Tottenham Court Road, London. Another instrument of this kind, the “Curve Rule” is sold by Mr. W. Harling, 47 Finsbury Pavement, E.C., and is figured here.

Flexible Curves.

Harling’s J. R. B. Curve Rules.

In dealing with such approximate curves as one finds among the lineations of finger-prints, one is not supposed to apply strictly mathematical principles. The lines, for example, have breadth, but not quite invariable breadth. We must, therefore, avoid treating them, as a beginner fresh from the schools is apt to do, as ideal concepts. The simpler terms, however, as used by a teacher of drawing, with the provisos already hinted at, will serve very well to guide one’s efforts, or to explain one’s own conceptions before a magistrate or a jury.

Besides the congruity of the curves, one has further to test the single lineations, their junctions, number, and character. An excellent way to envisage these is to make alternate linings with blue and red pencil, to represent them as they seem. To do this effectively one may single out a special measured square, or circle, or parallelogram, of the enlarged figure. Proceed then, quite ignoring, if need be, all great curvatures, to consider the lines as simple curved or straight lines, and analyse them into composing elements, like twigs of a tree or the characteristics of a runic alphabet. The result will be, perhaps, like the figure on the next page.

It will now be quite easy to orient, or place correctly in space, the corresponding part of the other print – if it really does correspond – and a similar “rune” should result. One may afterwards follow out each recognized lineation into further complexities or joinings, as you might trace out a railway line with its various junctions in a map.

Diagrammatic Analysis of Lineations in a Restricted Section.

A photographic enlargement, meant for forensic use, ought not to be marked or soiled in any way, but dots of coloured chalk or ink might be placed along the margins to denote where imaginary ruled lines might begin or end. One might also use glazed tissue paper, ruled in squares, or with eccentric circles like the mileage lines in a map of London. By the use of these placed over the figure one might verify particular coincidences or demonstrate discrepancies.

When the skin-pattern is impressed upon soft sealing-wax, clay, putty, and so on, the relievo image produced is different in this way from an ordinary ink-printed pattern. The convex ridges are now concave furrows, while the hollows are changed into heights.

In both kinds of impressions a reverse or mirror pattern is produced, a matter of some practical importance. This effect may, or may not again be reversed in the photographic process. It is not impossible, in such circumstances, that a suspect’s finger might be confused with a resembling “mirror” pattern, which was really not his own.

I have thought that the word verso, used technically for the reverse of a coin or medal, might be usefully employed in dactylography for the reverse or mirror image of a finger-pattern when printed. A technical word for the indented impression made by a finger on wax and the like is also wanted. Now geologists use -lite as a terminal to express the impression or cavity which had been formed in a rock, when soft, by the impressed body of an organism. Hence the word dactylolite might be used to denote an indented impression of a finger.

Kew Micrometer.

In making measurements of exhibits, the Kew micrometer devised by Sir Joseph Hooker is of much service. It is figured here, and has the useful quality of rendering measurements at the same time in both the English and decimal systems.

For the method of encircling suspect smudges, either before or after enlargement, and measuring from one fixed centre by the Kew micrometer or ordinary compasses, I have devised a disc of glass such as is used in microscope slides, and about the size of half-a-crown. In the centre is a conical pit into which one leg of the compass rests. Precise centring is thus obtained without the slightest risk of damaging the photographic or other exhibit by the sharp point of the compasses, which have, at the same time, free swing. These were prepared for me by Mr. Franks, optician, Stoke-on-Trent, and cost very little.

Glass Disc Centred (enlarged).

In all measurements close to a fork or junction, as in the crook of the letter Y, care must be taken in counting the lines below or above the fork. Ambiguity readily arises, with a train of resulting discrepancies. Other ambiguities also occur which require mention in a word or two. In deciphering an ancient manuscript blurred, mouldy, mayhap worm-eaten, doubts may arise as to which of two or three possible words or letters may have been intended. One looks for some rationality in the author’s writing, but in finger-prints there can be no such help. In manuscripts the problem may not directly be as to a word, but only as to a letter, but that single letter, read differently, may change the tenor of a passage. Is to be read as C or as G or as O? Is to be read as E or as B? So Fork is liable to be read as Pork.

Now, a very similar difficulty frequently occurs in reading a blurred finger-print, and such evidence should be scrutinized with the greatest vigilance, and all really doubtful cases should be discarded as useless in evidence. While the obscurity is sometimes merely due to defective printing, there are several patterns of frequent occurrence which are liable to be read variably. This was discussed at some length in chapter iii. of the Guide. There is a tendency so to view blots or blurs in such a case, that the cloudy spots become a weasel or even a whale. In Japan there are artists’ wine-parties, where a common game is to make an accidental splash of ink or colour, which is passed on to the next guest, who in turn converts it by one or more strokes of the brush into a figure of some character. Some years ago, I gave to a young men’s meeting a lecture on Ghosts, in which I showed a collection of ink-splashes produced without design, some of which were quite strikingly artistic in their suggestive impressionism. Hence the importance of clear printing, vigilant scrutiny of exhibits to be compared, and the attention of a well-informed judge and intelligent jury.

In certain circumstances, when a suspected person has been arrested abroad or at a distance, it may be desirable to compare his fresh finger-prints broadly with that of some well-known criminal whose register has been long in the hands of the police. This want led me to suggest, in 1905, that photo-telegraphy, in one of its forms, might be brought into use. Many improvements have been made since then, and it is now, I think, quite feasible to secure and transmit to a great distance outline lineations quite good enough for use at a preliminary enquiry, previous to a remand or committal.

CHAPTER VI
PERSISTENCE OF PATTERNS

A human finger, in ordinary circumstances, may preserve, unimpaired, not only its general pattern of lineations, sometimes very intricate, during its owner’s lifetime, but the minutest details also may be discerned after thirty or forty years, quite unchanged as elements of a pattern, and very likely for a longer period, though scientific observation has not extended much beyond that limit. Long immersion, after death, in water, till the skin is quite sodden, does not readily destroy, does not even greatly obscure, the lineations for the purpose of comparison with earlier printed records of them, and one can still read into finger-print type, so to speak, the lineations of an Egyptian mummy.

When first I ventured to call the attention of the scientific world to the patterns of finger-prints in 1879 or 1880, I suggested that the ancient mummies of Egypt might possibly be found to have retained those features sufficiently to be studied. I had no opportunity of obtaining access to such remains in order to test the point, but on returning to England I found that anticipation to be amply justified, as anyone may verify by a visit to the British Museum. The skin of a mummy is contracted, hard, and wrinkled, but one may trace the lineations through all their loops, joinings, ramifications and whorls, with great distinctness. So that it follows, did an Egyptian register of finger-prints exist, we might unearth the names and titles or deeds of some of those men who lived several thousands of years ago.

There is nothing, so far as has yet been observed, to mark their race out as essentially different from our own, nor do any ancient finger-prints look unlike those of present-day people’s.

The ridges on toes and fingers are visible in children born prematurely, even at a very early period, as I have observed in the practice of my profession, and as soon as the lineations are at all discernible they are of human type. So far as has yet been observed, we do not find that the growing human embryo repeats a history of finger-patterns, beginning at an earlier and lowlier biological stage, as is sometimes contended to be the case in regard to some other organic structures undergoing development.

The efforts I first made to investigate the problem of permanence were chiefly directed to the earlier periods of life, as presenting the greatest likelihood of variation in patterns during rapid growth. A large number of Japanese children, and also some thirty-five or more children of European parentage, in ages from five to ten, were minutely examined time after time during a period of two years – some of them again at longer intervals – without a single variation being detected. The lines and patterns in the fingers of growing children broaden out as the infant grows, but the ideal form – so to speak – of the pattern itself, retains full sway. To grasp this conception clearly is almost the whole science of finger-print identification.

During that period, some of those children suffered severely from scarlet fever, which, as a new disease, took a severe form in Japan, and the desquamation, or skin-peeling, was unusually severe, so that in those cases the test was a severe one. On several occasions I have called attention to the possibility of severe desquamation being followed by some change of patterns, and I still think this subject merits the attention of medical men, but no actual fact illustrating the apparent danger has yet been brought under notice. This may, however, be simply the result of a high degree of inattention to a subject which medical men do not seem to have interested themselves in until very recently. In acromegaly, a disease in which the fingers take on gigantic features, one might expect to find a very notable change of patterns, perhaps the addition of fresh lineations, but after some attempts to collect information not one single example of the kind has yet reached me.

Besides testing growing children in the manner I have stated, many Japanese medical students between the ages of twenty and thirty were made use of in this way. The ridges were carefully shaved by razors, or smoothed away by sand-paper, emery dust, or pumice stone, so that no distinct patterns could be traced. The same tests were applied to my own fingers and to those of one or two medical friends who were quite sceptical as to the continuity of the patterns. Many of the patients at the hospital, or out-door dispensary, were also induced to submit, but not a single instance of variation in the patterns was ever brought to light. My own fingerprints have not varied since that date, a period of fully thirty years. However smooth the surface had been made, the old design came up again with perfect fidelity, yielding exactly the same imprints as before, subject only to those very minor variations already described in a previous chapter, to which even engravings are subject. Up to the period of my final return to England in 1887, a period of nearly nine years, enthusiastic and vigilant observation of this point gave me complete confidence in the permanence of finger-print patterns as a basis of personal identification. With the exception of acromegaly and skin-peeling after acute fevers, I can conceive of no biological reason why changes might be anticipated in those patterns, and up to the present no evidence has reached me that even those conditions do effect pattern changes. In old age the ridges shrink somewhat, and wrinkles here and there betray the drying up of tissues, which facts are revealed in printed impressions by fine white lines, often cutting across the lineations, not unlike those which occur in box-wood engravings, where hair-like lines betray some cleavage of the wood. In such a case the value of the pattern is not affected as a proof of identity. One may go beyond that, and say that, if after a lapse of forty years or so the old pattern is now crossed by wrinkles which were not there in youth, the two prints are from the same individual.

Other observers – Sir Francis Galton, Sir William Herschel, and the police of this and other countries – have accumulated a vast store of conclusive evidence on this point.

We are now amply justified in assuming that, for all practical purposes of identification, the patterns on human fingers are, throughout life, persistent and unchangeable. Such slight and transient changes – not due to mere variations of pressure, inking, and the like, as they usually are – are no more likely to invalidate an identification than a new freckle or pimple on a man’s face would make him unrecognizable by his intimate friends.

Dr. J. G. Garson, in an article in the Daily Express of July 20th, 1905, writing on this subject, which he has carefully studied, said: —

“It is now a well ascertained fact that every person bears on his fingers as certain proof of his identity as he does on his face. The latter is, however, that part of his anatomy by which he is most readily identified by the world at large, though to his intimate friends other particulars about him may characterise him equally strongly. By means of the eye, the tout ensemble of the countenance is registered upon the mind, generally regardless of details respecting the actual form of each particular feature – in short, a person is recognized and identified by exactly the same psychological process as a printed or written word is read without first spelling it.”

It must be clear to any student of the subject that persistence of patterns must become the basis of identification in this way, and that persistence is now as firmly established as anything can be as to living creatures.

Sir Edward Henry, in his Finger-Prints, says (p. 17, 3rd edition): “Impressions being required for permanent record, their utility must, in great measure, be contingent upon the persistence through long periods of time, of the general form of the pattern and of the details of the ridges constituting it.” No such stability has yet been shown to exist in regard to any other part of the body. The bones change very greatly, not only in size, but in shape, texture, and mechanical conditions through life. Even the ordinary features and expression of a human being by no means can be said to remain uniform. One sees a friend during many short intervals, and is not finely observant of minute changes that in a decade or two amount collectively to an almost complete transformation of the man’s whole face and figure. The photographic system of identification, although serving a purpose now and then, was found, therefore, to be untrustworthy.

My revered teacher, Lord Lister, noted the slow migrations of the pigmentary particles that make the web-like patterns on a frog’s foot. I have observed similar but still slower changes in ordinary freckles on a human hand. The white spots of leucoderma – a skin-disease that used to be confused with leprosy, from which it entirely differs – are often bounded with dark borders, into which the pigment particles have migrated from the white spots. A negro’s skin sometimes becomes white where a fly-blister has been applied, as a fair-skinned person is often marked with a dark patch after a similar application. The pigment particles move to and fro like living things, though very slowly, and the marks they collectively make on a living body are not fixed and stable. Again, we have seen that the police used to record the position of wens, tumours, tattoo marks and the like. But tumours are now often removed through the line of natural creases, or wrinkles, leaving very faint traces, if any, behind.

An official in Japan had a large wen on his forehead, which disfigured him greatly. He was getting elderly, and told me, when friends brought him, that he would as soon have the wen as a scar. I got him to consent to have it removed through the natural wrinkle in the forehead, after which it left no visible trace at all.

A curious case was that of a man whose back and shoulders were adorned by a large collection of a certain kind of tumour varying from the size of a chestnut to that of a hen’s egg. They all disappeared, without the use of the knife, leaving no scar behind, and only a slight lowering and thinning of the skin.

Even scars, themselves, sometimes very unsightly ones, tone away to a large extent, till they cease to be at all conspicuous. The colour of the hair changes greatly in some people at the various stages of life. Certain diseases, too, such as malarious affections, the action of the sun, and certain employments, change the complexion in a very remarkable way.

What the pole-star used to be in navigation, fingerprint patterns are now become for all serious purposes of practical identification.